Radiographic image capturing apparatus

ABSTRACT

A radiographic image capturing apparatus includes: a readout IC equipped with a plurality of readout circuits connected to signal lines, respectively; a power source circuit which supplies a power to the readout IC; and a discharge circuit disposed on a path through which the power source circuit supplies the power to the readout IC, the discharge circuit being is capable of connecting the path and a GND to each other. The discharge circuit connects the path and the GND during a sleep mode.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S. patentapplication Ser. No. 14/717,300, filed on May 20, 2015, the entirecontents of which are incorporated herein by reference. The Ser. No.14/717,300 application claimed the benefit of the date of the earlierfiled Japanese Patent Application No. 2014-105793 filed May 22, 2014,priority to which is also claimed herein, and the contents of which arealso incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a radiographic image capturingapparatus, and especially to a radiographic image capturing apparatusincluding a plurality of radiation detecting elements two-dimensionallyarranged.

2. Description of Related Art

Heretofore, various kinds of radiographic image capturing apparatuseshave been developed, such as a so-called direct type radiographic imagecapturing apparatus which causes detecting elements to generate electriccharges depending on a dose of irradiated radiation such as X-ray andconverts the electric charges into electrical signals, and a so-calledindirect type radiographic image capturing apparatus which causes ascintillator or the like to convert irradiated radiation into otherwavelength light such as visible light and then causes photoelectricconversion elements such as photodiodes to generate electric chargesdepending on energy of converted and irradiated light and converts theelectric charges into electrical signals (i.e. image data). With regardto the present invention, the detecting elements of the direct typeradiographic image capturing apparatus and the photoelectric conversionelements of the indirect type radiographic image capturing apparatus arecorrectively referred to as radiation detecting elements.

The radiographic image capturing apparatus of this type has been knownas a Flat Panel Detector (FPD), and has been heretofore configured as aso-called exclusive-machine type (also called as a fixed type, etc.)configured integrally with a support base. Recently, there has beendeveloped and come into practical use a portable radiographic imagecapturing apparatus which houses the radiation detecting elements andthe like in a housing so that those elements and the like becomeportable.

In such a radiographic image capturing apparatus, as illustrated in FIG.3 to be mentioned later for example, generally a plurality of radiationdetecting elements 7 are arranged in the state of a two-dimensionalmatrix on a detecting section P. When the radiographic image capturingapparatus is irradiated with radiation through a not-illustrated patientas an object at the time of imaging, the radiation detecting elements 7generate the electric charges. To each of the radiation detectingelements 7, a switch element composed of a Thin Film Transistor(hereinafter referred to as a TFT) 8 and the like is connected. In areadout processing of image data D after the imaging, when the TFT 8 isturned on so that the electric charges accumulated in the radiationdetecting elements 7 are discharged into signal lines 6, the electriccharges flow into readout circuits 17 through the signal lines 6, andare read out as electric charge data D in the readout circuits 17. Thereadout processing of the image data D will be described later.

Meanwhile, in the case that imaging using the radiographic imagecapturing apparatus is not performed at least for a while, the powerapplied to respective functional sections such as the readout circuits17 of the radiographic image capturing apparatus is wasted. Especiallyin the above-described portable radiographic image capturing apparatusincluding a battery, if the power is thus wasted, the battery would beconsumed earlier, the number of time of the imaging on one batterycharge would be reduced, and imaging efficiency would be reduced. Thosehave been problems.

For this reason, there have been not a little radiographic imagecapturing apparatuses configured to have an imaging mode including atleast: a wake up mode in which the power is applied to the respectivefunctional sections so that the imaging can be performed; and a sleepmode in which the power is applied to required minimum functionalsections and the imaging cannot be performed, wherein the imaging modecan be switched between these modes (e.g. see Japanese PatentApplication Laid-open No. 2010-268171). The above-described readoutcircuits 17 consume relatively large power at the time of the readoutoperation of the image data D and the like. For this reason, in thesleep mode, generally the radiographic image capturing apparatus doesnot perform at least the readout operations in the readout circuits 17.

In the meantime, according to the research by the inventor, it has beenfound that when the imaging is performed after the power mode of theradiographic image capturing apparatus 1 is switched to the sleep modeand then switched to the imagable mode again, sometimes image unevennessand/or stripe pattern appear, though only slightly, in a radiographicimage I generated based on the image data D which has been read outafter the imaging (see FIG. 7). In FIG. 7, the image unevenness and thestripe pattern appearing in the radiographic image I are emphaticallyillustrated.

As described later, generally a predetermined number (e.g. 128, 256,etc.) of the readout circuits 17 are provided in one readout IC 16 (seeFIG. 3 to be mentioned later), and a necessary number of readout ICs 16are arranged in parallel depending on the number of signal lines 6 orthe like. According to the research of the inventor, as illustrated inFIG. 7, the image unevenness in the radiographic image I appears in eachof regions R1, R2, R3, R4, . . . corresponding to the readout ICs 16,respectively, and the strip pattern appears in positions correspondingto the readout circuits 17.

Concretely, the signal lines 6 are connected to the readout circuits 17,respectively, and the predetermined number of the signal lines 6 areconnected to each of the readout ICs 16, as described above. When payingattention to each of regions R1, R2, R3, R4, . . . in the radiographicimage I corresponding to the respective readout ICs 16, a certain offsetis superimposed on the image data D of pixels within each one of theregions R. The certain offset is different according to each of thereadout ICs 16. The superimposed offset appears as the image unevennessin each of regions R1, R2, R3, R4, . . . . Additionally, it has alsobeen found that offsets are superimposed on the image data D of pixelscorrespondingly to the signal lines 6 connected to the readout circuits17, respectively, which offsets appear as the stripe pattern in theradiographic image I.

As a result of accumulation of research by the inventor, the cause ofsuperimposition of the offset which causes image unevenness and/orstripe pattern on the image data D has been found, and also theconfiguration to prevent such a phenomenon from occurring has beenfound.

SUMMARY OF THE INVENTION

The present invention is made in view of the foregoing problems, and anobject of the present invention is to provide a radiographic imagecapturing apparatus which can accurately prevent an offset causing imageunevenness and/or stripe pattern from being superimposed on image dataeven when the power mode is switched from the sleep mode to the imagablemode and then an imaging is performed.

In order to achieve the above object, according to one aspect of apreferred embodiment of the present invention, there is provided aradiographic image capturing apparatus including: a plurality ofradiation detecting elements arranged two-dimensionally; a plurality ofsignal lines each connected to each of the radiation detecting elements;a readout IC equipped with a plurality of readout circuits connected tothe signal lines, respectively; a power source circuit which supplies apower to the readout IC; and a discharge circuit disposed on a paththrough which the power source circuit supplies the power to the readoutIC, the discharge circuit being capable of connecting the path and a GNDto each other, wherein the radiographic image capturing apparatus isconfigured so that an imaging mode can be switched at least between awake up mode in which the power is supplied to at least one functionalsection so that an imaging can be performed, and a sleep mode in whichthe power is supplied to a required minimum functional section of thefunctional section and the imaging cannot be performed, and thedischarge circuit connects the path and the GND to each other during thesleep mode.

According to the radiographic image capturing apparatus

having such a system, the electric charges remaining in the power sourcecircuit, readout IC and sensor panel can proactively flow out toward theGND and can be accurately removed via the discharge circuit during thesleep mode. Therefore, even when the power mode is subsequently switchedfrom the sleep mode to the imagable mode and then the imaging isperformed, the offsets due to the residual electric charges can beaccurately prevented from being superimposed on the image data, and theimage unevenness and/or stripe pattern can be accurately prevented fromappearing in the radiographic image I generated based on the read-outimage data and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the appended drawings, andthus are not intended as a definition of the limits of the presentinvention, and wherein:

FIG. 1 is a cross-section view of a radiographic image capturingapparatus;

FIG. 2 is a plan view illustrating a configuration of a substrate of theradiographic image capturing apparatus;

FIG. 3 is a block diagram illustrating an equivalent circuit of theradiographic image capturing apparatus;

FIG. 4 is a block diagram illustrating an equivalent circuit for onepixel constituting a detecting section;

FIG. 5A is a block diagram illustrating a configuration example of adischarge circuit;

FIG. 5B is a block diagram illustrating a configuration example of apart including the discharge circuit, a power source circuit, etc. ofthe radiographic image capturing apparatus according to this embodiment;

FIG. 6 is a graph illustrating a time shift of a voltage applied to eachradiation detecting element in the case of Variation 1-2; and

FIG. 7 is a diagram for explaining about image unevenness and/or stripepattern appearing in a generated radiographic image.

PREFERRED EMBODIMENT OF THE PRESENT INVENTION

Hereinafter embodiments of a radiographic image capturing apparatusaccording to the present invention will be described with reference tothe drawings.

Incidentally, as a radiographic image capturing apparatus of the presentinvention, a so-called indirect type radiographic image capturingapparatus which is equipped with a scintillator or the like and convertsirradiated radiation into other wavelength light such as visible lightto obtain an electrical signal will hereinafter be described. However,the present invention can also be applied to a so-called direct typeradiographic image capturing apparatus which directly detects radiationwith radiation detecting elements without the scintillator or the like.

Moreover, a case that the radiographic image capturing apparatus is aso-called portable type will be described, but the present invention canbe applied to a so-called exclusive-machine type radiographic imagecapturing apparatus integrally formed with a support base and the like.

Basic Configuration

First, a basic configuration and the like of the radiographic imagecapturing apparatus of this embodiment will be described. FIG. 1 is across-section view of the radiographic image capturing apparatus of theembodiment, and FIG. 2 is a plan view illustrating the configuration ofthe substrate of the radiographic image capturing apparatus.

In the embodiment, the radiographic image capturing apparatus 1 has ahousing 2 including a radiation incident surface R on a radiationirradiation side, the housing 2 containing a sensor panel SP composed ofa scintillator 3, a sensor substrate 4, etc. Although illustration isomitted in FIG. 1, an antenna 41 (see FIG. 3 to be mentioned later) fortransmitting/receiving data, signals, etc. to/from externaldevices/apparatuses in a wireless system, and a connector fortransmitting/receiving them in a wire system are provided on a sidesurface or the like of the housing 2.

As illustrated in FIG. 1, a base 31 is disposed in the housing 2, andthe sensor substrate 4 is disposed on a radiation-incident-surface Rside (hereinafter simply referred to as an upper-surface side, etc., inconformity to a vertical direction in the drawings) of the base 31through a not-illustrated lead thin film or the like. Additionally,radiation detecting elements 7 and the like are disposed on theupper-surface side of the sensor substrate 4, and furthermore thescintillator 3 is disposed on them, the scintillator 3 converting theirradiated radiation into light such as visible light so as to emit thelight to the radiation detecting elements 7. Incidentally, thescintillator 3 is attached to a scintillator substrate 34.

On a lower surface side of the base 31, there are disposed a PCBsubstrate 33 on which electronic components 32 and the like arearranged, a battery 24, and so on. The sensor panel SP is thus composedof the base 31, the sensor substrate 4, and so on. Furthermore, in theembodiment, a cushioning 35 is provided between the sensor panel SP andeach of the sides of the housing 2.

The sensor substrate 4 of the embodiment is composed of a glasssubstrate, and as illustrated in FIG. 2, a plurality of scanning lines 5and a plurality of signal lines 6 are arranged so as to cross each otheron the upper surface 4A (i.e. the surface facing the scintillator 3) ofthe sensor substrate 4. In small areas S divided by the scanning lines 5and the signal lines 6 on the surface 4A of the sensor substrate 4, theradiation detecting elements 7 are disposed, respectively.

The whole of the small areas S divided by the scanning lines 5 andsignal lines 6 and including the radiation detecting elements 7 arrangedin the state of a two-dimensional matrix, namely a region indicated withchain lines in FIG. 2, is defined as a detecting section P. In theembodiment, photodiodes are used as the radiation detecting elements 7,but, for example, also phototransistors or the like may be used.

Here, a circuit configuration of the radiographic image capturingapparatus 1 will be described. FIG. 3 is a block diagram illustrating anequivalent circuit of the radiographic image capturing apparatus 1 ofthe embodiment, and FIG. 4 is a block diagram illustrating an equivalentcircuit of one pixel constituting the detecting section P.

To a first electrode 7A of each of the radiation detecting elements 7, asource electrode 8S (see “S” in FIGS. 3 and 4) of the TFT 8 as theswitch element is connected. A drain electrode 8D and a gate electrode8G (see “D” and “G” in FIGS. 3 and 4) of the TFT 8 are connected to eachof the signal lines 6 and each of the scanning lines, respectively.

The TFT 8 becomes on-state when an ON voltage is applied to the gateelectrode 8G from a later-described scan driving member 15 via each ofthe scanning lines 5, and causes the electric charge accumulated in theradiation detecting member 7 to be discharged to each of the signallines 6 via the source electrode 8S and the drain electrode 8D. The TFT8 becomes off-state when an OFF voltage is applied to the gate electrode8G via each of the scanning lines 5, and stops the discharge of theelectric charge to each of the signal lines 6 from the radiationdetecting member 7 so that the electric charge is accumulated in theradiation detecting element 7.

In the embodiment, as illustrated in FIGS. 2 and 3, a bias line 9 isprovided for each column of the radiation detecting members 7 andconnected to a second electrode 7B of each of the radiation detectingmembers 7. A plurality of bias lines 9 are connected to a tie line 10 atthe outside of the detecting section P of the sensor substrate 4. Thetie line 10 is connected to a bias power source 14 (see FIGS. 3 and 4)via an input/output terminal 11 (also referred to as a pad, etc.; seeFIG. 2) so that a reverse bias voltage is applied to the secondelectrode 7B of each of the radiation detecting members 7 from the biaspower source 14 via the tie line 10 and each of the bias lines 9.

Incidentally, in the embodiment, a not-illustrated flexible circuitsubstrate is connected to each of the input/output terminals 11, theflexible circuit substrate including a chip such as a later-describedreadout IC 16 and a gate IC constituting a gate driver 15B of the scandriving member 15, the chip being incorporated on a film. The scanninglines 5, the signal lines 6, and the tie line 10 of the bias lines 9 onthe sensor substrate 4 are electrically connected to electroniccomponents 32 and the like (see FIG. 1) disposed on the back side of thesensor panel SP via the flexible circuit substrate.

In the scan driving member 15, the ON and OFF voltages are supplied tothe gate driver 15B from the power source circuit 15A via a wiring 15C.The voltage to be applied to each of lines L1 to Lx of the scanninglines 5 is switched between the ON voltage and the OFF voltage by thegate driver 15B.

Each of the signal lines 6 is connected to each of the readout circuits17 contained in each of the readout ICs 16 via each of the input/outputterminals 11. The readout circuit 17 of the embodiment is mainlycomposed of an amplifier circuit 18, a correlated double samplingcircuit 19, etc. The readout IC 16 further includes an analogmultiplexer 21 and an A/D convertor 20. In FIGS. 3 and 4, the correlateddouble sampling circuit 19 is written as “CDS”.

The amplifier circuit 18 of the embodiment is composed of a chargeamplifier circuit including an operational amplifier 18A, and acapacitor 18B and electric-charge reset switch 18C each of which isconnected in parallel with respect to the operational amplifier 18A. Toan inverted input terminal on an input side of the operational amplifier18A of the amplifier circuit 18, each of the signal lines 6 isconnected. The electric-charge reset switch 18C of the amplifier circuit18 is connected to a control member 22, and controlled to be turnedon/off by the control member 22. Incidentally, the power source circuit51 supplies the power to the operational amplifier 18A and the like.This point will be described later.

At the time of the readout processing of the image data D from theradiation detecting elements 7 after imaging, when the TFTs 8 of theradiation detecting elements 7 become on-state while the electric-chargereset switch 18C of the amplifier circuit 18 in the readout circuit 17is in the off state, the electric charges discharged from the radiationdetecting elements 7 via the TFTs 8 pass though the signal lines 6 toflow into the capacitors 18B of the amplifier circuits 18, and therebythe electric charges are accumulated in the capacitors 18B. Then each ofthe amplifier circuits 18 outputs a voltage value depending on aquantity of the electric charge accumulated in the capacitor 18B fromthe output side.

The correlated double sampling circuit 19 retains the output values fromthe amplifier circuit 18 before and after the flow of the electriccharges from the radiation detecting elements 7, and outputs adifference between these output values toward the downstream side as theimage data D having an analog value. Then the output image data D issequentially transmitted to the A/D convertor 20 via the analogmultiplexer 21 (see FIG. 3), sequentially converted into the image dataD having a digital value by the A/D convertor 20, and output to astorage member 23 and sequentially stored therein. Thus the readoutprocessing of the image data D is performed.

The control member 22 is composed of a computer including anot-illustrated Central Processing Unit (CPU), Read Only Memory (ROM),Random Access Memory (RAM), input/output interface, etc. which areconnected to a bus, and a Field Programmable Gate Array (FPGA), and soon. Alternatively, the control member 22 may be composed of a dedicatedcontrol circuit.

The control member 22 controls the operations of the respectivefunctional sections of the radiographic image capturing apparatus 1, forexample, controls the scan driving member 15 and/or the readout circuit17 so that the readout processing of the image data D is performed asdescribed above. As illustrated in FIGS. 3 and 4, the storage member 23composed of a Static RAM (SRAM), Synchronous DRAM (SDRAM), or the likeis connected to the control member 22. Moreover, to the control member22 of the embodiment, the above-described antenna 41 is connected, andalso the battery 24 which supplies the necessary power to the functionalsections such as the scan driving member 15, readout circuit 17, storagemember 23, bias power source 14, etc. is connected.

In the embodiment, the radiographic image capturing apparatus 1 isconfigured so that the imaging mode can be switched at least between awake up mode in which the power is supplied to the functional sectionssuch as the control member 22 so that imaging can be performed, and asleep mode in which the power is applied to required minimum functionalsections and the imaging cannot be performed.

At that time, the readout circuit 17 consumes relatively large power atthe time of the readout operation of the image data D and the like asdescribed above. Accordingly, though the sleep mode can take variousforms, at least the readout operation by the readout circuit 17 is notperformed in the sleep mode of the embodiment.

Configuration and the Like Specific to the Present Invention

Next, the configuration specific to the present invention in theradiographic image capturing apparatus 1 of the embodiment will bedescribed.

As described above, when the imaging is performed after the power modeof the radiographic image capturing apparatus 1 is switched from thesleep mode to the imagable mode, some offset is superimposed on theimage data D which has been read out after the imaging, and sometimesimage unevenness and/or stripe pattern appear, though only slightly, inthe radiographic image generated based on the image data D (e.g. seeFIG. 7).

The inventor has been doing the research about the cause of such aphenomenon, and the following things have come to light. Even when theimaging is performed by the radiographic image capturing apparatus 1 inthe imagable mode, and after the imaging, the power mode of theradiographic image capturing apparatus 1 is switched to the sleep modeso that the radiographic image capturing apparatus 1 becomespower-saving state, the electric charges in the functional sections ofthe radiographic image capturing apparatus 1 are not removedimmediately, because the electric charges remain in portions, forexample, where parasitic capacitance is formed, the portions being, forexample, on the side of the detecting section P (see FIG. 3) includingthe radiation detecting elements 7, scanning lines 5 and signal lines 6,on the side of the readout IC 16, and/or on the side of theafter-described power source circuit 51 (see FIGS. 5A and 5B to bementioned later) which supplies the power to the readout IC 16 and thelike.

Because a removal efficiency of the residual electric charge isdifferent according to each of the readout ICs 16, the value of theoffset to be superimposed on the image data D, the offset being due tothe residual electric charge, becomes different according to each of thereadout ICs 16. Such an offset appears as the image unevenness in eachof regions R1, R2, R3, R4, . . . of the radiographic image I, theregions corresponding to the readout ICs 16, respectively. Moreover,because the removal efficiency of the residual electric charge is alsodifferent according to each of the readout circuits 17, the value of theoffset to be superimposed on the image data D, the offset being due tothe residual electric charge, becomes different according to each of thereadout circuits 17. This seems the reason why the stripe patternscorresponding to the readout circuits 17 appear in the radiographicimage I.

Consequently, the present invention adopts the configuration where adischarge circuit is provided on a path (hereinafter referred to as apower supplying path) through which the power source circuit 51 suppliesthe power to the readout IC 16. The power supplying path can beconnected to a GND by the discharge circuit. The discharge circuit makesthe power supplying path and the GND connected to each other while thepower mode of the radiographic image capturing apparatus 1 is set to thesleep mode.

Hereinafter the configuration including the discharge circuit and thepower source circuit 51 will be described in detail. FIG. 5A is a blockdiagram illustrating a configuration example of the discharge circuit,and FIG. 5B is a block diagram illustrating a configuration example of apart including the discharge circuit, power source circuit, etc. in theradiographic image capturing apparatus of the embodiment. Incidentally,though only the power source circuits 51 and power supplying paths 50for supplying the power to the readout IC 16 are illustrated in FIG. 5B,it is needless to say that other power source circuits, power supplyingpaths and the like for supplying the power to other functional sectionsof the radiographic image capturing apparatus 1, such as the bias powersource 14 and the power source circuit 15A of the scan driving member15, can be arbitrary provided.

As illustrated in FIG. 5A, the discharge circuit 60 of the embodiment isdisposed on the power supplying path 50 through which theafter-described power source circuit 51 supplies the power to thereadout IC 16. On a wiring 61 connecting the power supplying path 50 tothe GND in the discharge circuit 60, there is provided a switch element62 which is composed of, for example, a Field Effect Transistor (FET).The switch element 62 is controlled to be turned on/off by controlsignals from the control member 22 (see FIG. 3 and the like).Additionally, a resistance 63 is disposed on the wiring 61 whichconnects the power supplying path 50 to the switch element 62 so thatthe electric discharges are prevented from flowing into the GND at oncewhen the switch element 62 is turned on.

In the embodiment, as illustrated in FIG. 5B, the power source circuit51 is disposed on a power source substrate 52. The above-describedbattery 24 which is composed of, for example, a lithium ion capacitorsupplies the power to the power source circuit 51. As the power sourcecircuit 51, there are provided a power source circuit 51A for supplyingthe power to an analog circuit such as the operation amplifier 18A ofthe amplifier circuit 18 in the readout IC 16, and a power sourcecircuit 51B for supplying the power to a digital circuit such as the A/Dconvertor 20 (see FIGS. 3 and 4) in the readout IC 16. In theembodiment, each of the power source circuits 51A, 51B is composed of aDC/DC convertor or the like, and outputs a predetermined voltage valueto each of the power supplying paths 50A, 50B.

Additionally, a constant voltage DC power source circuit 53 is disposedon the power supplying path 50A connected to the power source circuit51A. As the constant voltage DC power source circuit, for example, a LowDrop-Out regulator may be used.

Incidentally, FIG. 4 illustrates only the path through which the powersource circuit 51 (i.e. the power source circuit 51A in this case)supplies the power to the operational amplifier 18A of the amplifiercircuit 18 in the readout circuit 17, and the illustrations of a paththrough which the power source circuit 51A supplies the power to otheranalog circuits in the readout IC 16, a path through which the powersource circuit 51B supplies the power to the digital circuits in thereadout IC 16 such as the A/D convertor 20, and so on are omitted inFIG. 4. Also the constant voltage DC power source circuit 53, thedischarge circuit 60, etc. are omitted in FIG. 4.

In the embodiment, a substrate 54 including the constant voltage DCpower source circuit 53 is connected to the sensor substrate 4 (seeFIGS. 1 and 2) of the sensor panel SP via a flexible circuit substrate55. The readout ICs 16 are incorporated on the film of the flexiblecircuit substrate 55. The required number of the readout ICs 16 areprovided correspondingly to the number or the signal lines 6 or thelike, as described above.

In the embodiment, the discharge circuit 60 illustrated in FIG. 5A isdisposed on the power supplying path 50A connecting the constant voltageDC power source circuit 53 and the readout IC 16 to each other. Thedischarge circuit 60 is disposed also on the power supplying path 50Bconnecting the power source circuit 51B for supplying the power to thedigital circuit and the readout IC 16 to each other.

Incidentally, though FIG. 5B illustrates the case that the dischargecircuit 60 on the power supplying path 50B is disposed on the substrate54, the discharge circuit 60 can also be disposed on the power sourcesubstrate 52 (i.e. in the vicinity of the power source circuit 51B). Thedischarge circuits 60 are thus disposed on the appropriate positions onthe power supplying paths 50A, 50B.

Operations

Next, the operations of the radiographic image capturing apparatus 1 ofthe embodiment will be described.

When the imaging is performed by the radiographic image capturingapparatus 1 while the power mode of the radiographic image capturingapparatus 1 is set to the imagable mode, if the power supplying path 50is connected to the GND, the power, which is to be supplied to thereadout IC 16 from the power source circuit 51, would be released to theGND. As a result, the readout IC 16 cannot accurately function, theimage data D cannot be read out from the radiation detecting elements 7,and the imaging cannot be accurately performed.

For this reason, the discharge circuit 60 does not connect the powersupplying path 50 to the GND when the power mode of the radiographicimage capturing apparatus 1 is set to the imagable mode. Concretely, thecontrol member 22 controls the switch element 62 (see FIG. 5A) of thedischarge circuit 60 so that it becomes off-state in the imagable mode.

The control member 22 switches the power mode of the radiographic imagecapturing apparatus 1 from the imagable mode to the sleep mode at theappropriate timing, such as the timing when the imaging is completed,and the timing when non-imaging state continues for a predeterminedtime. At that time, the control member 22 executes the control so thatthe switch element 62 of the discharge circuit 60 is turned on, andthereby the power supplying path 50 is connected to the GND.

When the discharge circuit 60 connects the power supplying path 50 tothe GND, the electric charges remaining on the side of the power sourcecircuit 51 (see FIG. 5B) flow into the discharge circuit 60 from thepower supplying path 50, and flow out toward the GND through the switchelement 62. The electric charges remaining on the side of the powersource circuit 51 are thus removed, by the discharge circuit 60, fromthe side of the power source circuit 51 accurately.

Moreover, when the discharge circuit 60 connects the power supplyingpath 50 to the GND, the electric charges remaining on the side of thereadout IC 16 (see FIG. 5B) flow into the discharge circuit 60 from thepower supplying path 50, and flow out toward the GND through the switchelement 62. The electric charges remaining on the side of the readout IC16 are thus removed, by the discharge circuit 60, from the side of thereadout IC 16 accurately.

In the meantime, the sensor panel SP has the configuration where atleast one insulating layer is disposed between adjacent components amongthe scanning lines 5, signal lines 6, radiation detecting elements 7,TFT 8, bias lines 9, and so on (see FIGS. 2 and 3) and the parasiticcapacitances are formed in various portions. For this reason, even whenthe power mode of the radiographic image capturing apparatus 1 isswitched to the sleep mode, the electric charges are trapped in theportions of the parasitic capacitances and remain therein, and cannotalways be removed easily.

However, when the discharge circuit 60 connects the power supplying path50 to the GND at the time of shift of the power mode from the imagablemode to the sleep mode as the embodiment, the electric charges remainingin the sensor panel SP flow into the readout IC 16 from the sensor panelSP via the signal lines 6 as illustrated in FIG. 5B, and the electriccharges, which has flowed into the readout IC 16, flow into thedischarge circuit 60 via the power supplying path 50 and flow out towardthe GND.

Accordingly, the configuration of the embodiment can accurately removethe electric charges remaining not only in the power source circuit 51and/or the readout IC 16 but also in the sensor panel SP so that theelectric charges flow out toward the GND via the discharge circuit 60and can be accurately removed.

As described above, because the removal efficiency of the residualelectric charges in the sleep mode is different according to each of thereadout ICs 16 or each of the readout circuits 17, a conventionalradiographic image capturing apparatus reaches the state that a residualamount of the electric charges which have not been removed during thesleep mode is different according to each of the readout ICs 16 or eachof the readout circuits 17.

If the power mode is switched from the sleep mode to the imagable modeand then the imaging is performed during the radiographic imagecapturing apparatus is in the above state, the offset to be superimposedon the image data D, the offset being due to the residual electriccharge, would become different according to each of the readout ICs 16so that the image unevenness appears in the radiographic image I, and/orthe offset to be superimposed on the image data D, the offset being dueto the residual electric charge, would become different according toeach of the readout circuits 17 so that the stripe pattern appears inthe radiographic image I (see FIG. 7).

On the contrary, the radiographic image capturing apparatus 1 of theembodiment has the configuration where the discharge circuits 60 areprovided on the power supplying paths 50, and the discharge circuit 60connects the power supplying path 50 to the GND while the power mode ofthe radiographic image capturing apparatus 1 is set to the sleep mode sothat the electric charges remaining in the power source circuit 51,readout IC 16, sensor panel SP, and so on are proactively removed towardthe GND.

According to the configuration, even when the removal efficiency of theresidual electric charges in the sleep mode is different according toeach of the readout ICs 16 or each of the readout circuits 17, thedischarge circuit 60 proactively makes the residual electric chargesflow out toward the GND, and thereby the electric charges are removedfrom the apparatus. Accordingly, the radiographic image capturingapparatus 1 can maintain the state that the electric charges hardlyremain in the power source circuit 51, readout IC 16, sensor panel SP,and so on while the sleep mode is continued.

After that, when the power mode is switched from the sleep mode to theimagable mode and then the imaging is performed, the offsets due to theresidual electric charges are not superimposed (or are hardlysuperimposed) on the image data D. Accordingly, the radiographic image Igenerated based on the read-out image data D does not include the imageunevenness caused by a difference in the removal efficiency of theresidual electric charges according to each of the readout ICs 16, orthe stripe pattern caused by a difference in the removal efficiency ofthe residual electric charges according to each of the readout circuits17.

Effects

As described above, according to the radiographic image capturingapparatus 1 of the embodiment, the discharge circuits 60 capable ofconnecting the power supplying path 50 and the GND to each other aredisposed on the power supplying paths 50 through which the power sourcecircuits 51 supply the power to the readout IC 16, and the dischargecircuit 60 connects the power supplying path 50 and the GND to eachother while the power mode of the radiographic image capturing apparatus1 is set to the sleep mode.

Thus, the electric charges remaining in the power source circuit 51,readout IC 16 and sensor panel SP can be accurately removed because thedischarge circuit 60 proactively makes the electric charges flow outtoward the GND during the sleep mode. Even when the power mode isswitched from the sleep mode to the imagable mode and the imaging isperformed after that, the offsets due to the residual electric chargescan be accurately prevented from being superimposed on the image data D,and the image unevenness and/or stripe pattern can be prevented fromappearing in the radiographic image I generated based on the read-outimage data D.

Incidentally, according to the research of the inventor, it has beenconfirmed that the radiographic image I includes no image unevenness orstripe pattern, or at least the image unevenness and/or stripe patterncannot be visually confirmed in the radiographic image I, when theradiographic image capturing apparatus 1 is actually configured to havethe configuration of the embodiment.

Others Such as Variations

The configuration of the part including the discharge circuit 60, powersource circuit 51, etc. of the radiographic image capturing apparatus 1illustrated in FIG. 5B is a mere example, and it is needless to say thatother necessary configurations such as a low pass filter can bearbitrary provided.

In the above embodiment, there is described the case that the controlmember 22 transmits the control signals to the switch element 62 (seeFIG. 5A) of the discharge circuit 60 so as to turn on/off the switchelement 62, when the power mode of the radiographic image capturingapparatus 1 is switched to the sleep mode or the imagable mode, so thatthe discharge circuit 60 connects the power supplying path 50 and theGND to each other and/or cuts the connection theirbetween.

Alternatively, for example, the configuration where the dischargecircuit 60 itself switches on/off of the switch element 62, on the basisof the signals for switching the power mode to the sleep or imagablemode transmitted from the control member, 22 so as to connect the powersupplying path 50 and the GND to each other or cut the connectiontheirbetween, may be adopted.

Some radiographic image capturing apparatuses 1 are configured so thatthe power is not supplied also to the control member 22 in the sleepmode. In such a case, for example, a configuration where the switchelement 62 of the discharge circuit 60 is automatically turned on/off inaccordance with the stop (in the case of the sleep mode) or theactivation (in the case of the imagable mode) of the control member 22may be adopted, instead of controlling the on/off of the switch element62 of the discharge circuit 60 by the control section 22 as describedabove.

Variation 1

As described above, according to the configuration where the dischargecircuits 60 are disposed on the power supplying paths 50 through whichthe power source circuits 51 supply the power to the readout IC 16, andwhere the discharge circuit 60 connects the power supplying path 50 tothe GND during the sleep mode, the electric charges remaining in thepower source circuit 51, readout IC 16, sensor panel SP, and so on areremoved.

Additionally, in order to remove the electric charges remaining in thesensor panel SP more accurately, it is possible to adopt a configurationwhere the bias power source 14 (see FIGS. 3 and 4) applies the reversebias voltages to each of the radiation detecting elements 7 via each ofthe bias lines 9 also in the sleep mode. According to the configuration,the electric charges remaining in the radiation detecting elements 7 canflow out toward the side of the bias power source 14 via the bias lines9 in the sleep mode, and thereby the electric charges can be accuratelyremoved from the radiation detecting elements 7.

Variation 1-1

In this regard, it is possible to adopt a configuration where the biaspower source 14 continues to apply the reverse bias voltage to theradiation detecting elements 7 during the sleep mode. According to theconfiguration, the reverse bias voltage can be continuously applied fromthe bias power source 14 to the radiation detecting elements 7 duringthe sleep mode. Therefore, the electric charges remaining in theradiation detecting elements 7 can flow out toward the side of the biaspower source 14 so as to be accurately removed from the radiationdetecting elements 7.

Variation 1-2

It is also possible to adopt a configuration where the bias power source14 applies the reverse bias voltage Vbias to each of the radiationdetecting elements 7 only for a predetermined time At every time thevoltage V applied from the bias power source 14 to each of the radiationdetecting elements 7 rises and reaches a set threshold Vth.

In this case, for example, if the power mode of the radiographic imagecapturing apparatus 1 is switched from the imagable mode to the sleepmode at time t0 as illustrated in FIG. 6, the voltage V applied from thebias power source 14 to each of the radiation detecting elements 7gradually rises from the reverse bias voltage Vbias. When the voltage Vreaches the threshold Vth, the bias power source 14 applies the reversebias voltage Vbias, which has been set to a voltage value lower than thethreshold Vth, to each of the radiation detecting elements 7 only forthe predetermined time At. Thus, the voltage V applied from the biaspower source 14 to each of the radiation detecting elements 7 rises andfalls between the reverse bias voltage Vbias and the threshold Vth.

According to such a configuration, the voltage V applied from the biaspower source 14 to each of the radiation detecting elements 7 becomesthe low voltage value within the range from the reverse bias voltageVbias to the threshold Vth during the sleep mode, and thereby it becomespossible to continuously apply the voltage having such a low voltagevalue to each of the radiation detecting elements 7 during the sleepmode. Therefore, the electric charges remaining in the radiationdetecting elements 7 can flow out toward the side of the bias powersource 14 so as to be accurately removed from the radiation detectingelements 7. Moreover, compared with the case of continuously applyingthe reverse bias voltage as Variation 1-1, electric power consumptioncan be further reduced.

Variation 1-3

Incidentally, it is also possible to adopt a configuration where thebias power source 14 applies the reverse bias voltage Vbias to each ofthe radiation detecting elements 7 only for the predetermined time At,at every predetermined time AT during the sleep mode, regardless of thevoltage V applied from the bias power source 14 to each of the radiationdetecting elements 7, instead of applying the reverse bias voltage Vbiasfrom the bias power source 14 to each of the radiation detectingelements 7 only for the predetermined time At every time the voltage Vapplied from the bias power source 14 to each of the radiation detectingelements 7 reaches the set threshold Vth during the sleep mode asVariation 1-2. In this case, the predetermined time AT is set to a timeaccording to which the voltage V applied from the bias power source 14to each of the radiation detecting elements 7 does not become equal toor more than the threshold Vth.

According to such a configuration, the voltage V applied from the biaspower source 14 to each of the radiation detecting elements 7 can besuppressed to be the low voltage value during the sleep mode, andthereby the electric charges remaining in the radiation detectingelements 7 can flow out toward the side of the bias power source 14 soas to be accurately removed from the radiation detecting elements 7.Moreover, the reverse bias voltage Vbias only have to be applied fromthe bias power source 14 to each of the radiation detecting elements 7only for the predetermined time At every time the predetermined time AThas passed during the sleep mode, the processing can be easilyperformed. Furthermore, compared with the case of continuously applyingthe reverse bias voltage Vbias as Variation 1-1, electric powerconsumption can be further reduced.

Variation 2

Alternatively, in order to more proactively remove the residual electriccharges from the radiation detecting elements 7 during the sleep mode,for example, it is also possible to adopt a configuration where the gatedriver 15B (see FIG. 3) of the scan driving member 15 sequentially orsimultaneously applies ON voltages to lines L1 to Lx of the scanninglines 5 during the sleep mode so that the electric charges are removedfrom the radiation detecting elements 7.

Similarly to the case of the readout IC 16 illustrated in FIG. 5B, thebattery 24 supplies the power also to the power source circuit 15A ofthe scan driving member 15 as illustrated in FIG. 3. When the power modeof the radiographic image capturing apparatus 1 is set to the imagablemode, the power source circuit 15A supplies the ON and OFF voltages tothe gate driver 15B, and the gate driver 15B switches the power to beapplied to each of lines L1 to Lx of the scanning lines 5 between the ONand OFF voltages. Thus, the ON or OFF voltage is applied to each oflines L1 to Lx of the scanning lines 5.

Because the supply of the power from the battery 24 to the power sourcecircuit 15A of the san driving member 15 is stopped in the sleep mode,the voltage applied from the gate driver 15B to each of lines L1 to Lxof the scanning lines 5 is in a floating state. The TFTs 8 do notcompletely become off-state because the gate driver 15B does not applyat least the OFF voltage to the scanning lines 5 in the sleep mode.Accordingly, the electric charges can outflow toward the side of thesignal lines 6 or the side of the bias lines 9 via the TFTs 8 in theabove-described state. However, the residual electric charges can beremoved from the radiation detecting elements 7 during the sleep mode bythe configurations of the above embodiments and Variations.

By proactively performing the removing process of the electric chargesfrom the radiation detecting elements 7 during the sleep mode, theresidual electric charges can be more accurately removed from theradiation detecting elements 7. Moreover, according to such aconfiguration, by more accurately removing the electric chargesremaining in the radiation detecting elements 7, the image unevennessand/or stripe pattern caused by the offsets due to the residual electriccharges can be prevented from appearing in the radiographic image I.

Incidentally, it is indisputable that the present invention is notlimited to the above embodiments and variations, and can be arbitrarychanged without departing from the spirit of the present invention.

The present U.S. patent application claims a priority under the ParisConvention of Japanese patent application No. 2014-105793 filed on May22, 2014, in which all contents of this application are disclosed, andwhich shall be a basis of correction of an incorrect translation.

What is claimed is:
 1. A radiographic image capturing apparatuscomprising: a plurality of radiation detecting elements arrangedtwo-dimensionally; a plurality of signal lines each connected to each ofthe radiation detecting elements; and a bias power source which appliesa reverse bias voltage to the radiation detecting elements, wherein theradiographic image capturing apparatus is configured so that an imagingmode can be switched at least between a wake up mode in which the poweris supplied to at least one functional section so that an imaging can beperformed, and a sleep mode in which the power is supplied to a requiredminimum functional section of the functional section and the imagingcannot be performed, and the bias power source applies the reverse biasvoltage to the radiation detecting elements in the sleep mode.
 2. Theradiographic image capturing apparatus of claim 1, wherein the biaspower source continuously applies the reverse bias voltage to theradiation detecting elements during the sleep mode.
 3. The radiographicimage capturing apparatus of claim 1, wherein the bias power sourceapplies the reverse bias voltage to the radiation detecting elementsonly for a predetermined time every time the voltage applied from thebias power source to the radiation detecting elements rises and reachesa set threshold.
 4. The radiographic image capturing apparatus of claim1 further comprising: a plurality of scanning lines; a scan drivingmember which switches a voltage applied to each of the scanning linesbetween an ON voltage and an OFF voltage; and a switch element connectedto each of the scanning lines, the switch element causing an electriccharge accumulated in each of the radiation detecting elements to bedischarged to each of the signal lines when the ON voltage is applied tothe switch element via the each of the scanning lines, wherein theradiographic image capturing apparatus performs processing to cause thescan driving member to sequentially or simultaneously apply the ONvoltage to each of the scanning lines during the sleep mode, so that theelectric charge is removed from each of the radiation detectingelements.